tert-Butyl acetate
A VOC-exempt ester solvent popular as a low-VOC thinner for urethanes and epoxies.
tert-Butyl acetate is an ester of acetic acid and tert-butanol that boils at about 98 °C. US EPA exempted it from the VOC definition in 2004 and later removed its special recordkeeping requirements.
t-BAc is used as a reducer and solvent in low-VOC polyurethane, epoxy and acrylic coatings, inks and adhesives, often blended with other exempt and non-exempt solvents to balance evaporation.
As an ester without hydroxyl groups, dry t-BAc is compatible with isocyanates. It evaporates faster than xylene and has good solvency for many coating resins.
Flammable; ventilate and control ignition sources. Some state and local air agencies do not exempt t-BAc and some health agencies have flagged its metabolite for review, so check local rules.
Treatment varies by agency. It is exempt under federal rules, but some California air districts have not exempted it. Always check the applicable local rule.
Urethane-grade t-BAc is commonly used, provided the coating manufacturer approves it.
